Stereoscopic image detection devices are known in the art. Such devices are required to obtain and provide a combination of small cross section and high image quality. It will be appreciated by those skilled in the art that high image quality, in general, is characterized by stereoscopic vision accuracy, color capabilities, high resolution and illumination requirements.
It is noted that conventional methods, which provide stereoscopic images, require a wider optical path than a monocular one. Such a widened optical path enlarges the cross-section required for the detection device considerably. Hence, the requirement for a small cross section is not maintained.
U.S. Pat. No. 5,527,263 to Zobel, et al., is directed to a dual optical path stereo endoscope with simple optical adjustment. U.S. Pat. No. 5,776,049 to Takahashi, is directed to a “Stereo Endoscope and Stereo Endoscope Imaging Apparatus” and provides a device which utilizes a combination of two optical paths with two charge coupled devices (CCD's), capable of variable zoom.
Auto-stereoscopic devices, which utilize one optical system to provide a stereo effect, are also known in the art. Such a device is provided in U.S. Pat. No. 5,603,687 to Hori et al., which is directed to a device with two parallel optical axes and two CCD units. Hori selected an asymmetrical approach, wherein one optical channel has a large aperture for light and details, and the other optical channel provides a parallax image for stereoscopic imagery to the proximal CCD.
U.S. Pat. No. 5,613,936 to Czarnek et al., is directed to a stereoscopic endoscope device which utilizes light polarization and time multiplexing, in order to transmit each different polarized image corresponding to left and right images multiplexed in time, through one optical channel that transfers images from the lateral side of the endoscope shaft. This endoscope has to be inserted deeper into the human cavity to receive a stereo image. It must also be used with a head mounted display device called “switched shutter glasses” that causes eye irritation. It is noted that according to Czarnek each image is received in 25% of the original quality. As much as 50% of the light received from the object, is lost due to polarization considerations and as much as 50% of the remaining information is lost due to channel switching.
U.S. Pat. No. 5,588,948, to Takahashi, et al., is directed to a stereoscopic endoscope. The stereo effect is produced by having a dividing pupil shutter, which splits the optical path onto the left and right sides, and the up and down sides. These sides are alternately projected on a proximal image pick up device, using time multiplexing. According to another aspect of this reference, a distal CCD is included, which is divided to left and right sides with a shading member separating them, for achieving space multiplexing.
U.S. Pat. No. 5,743,847 to Nakamura et al., is directed to a “Stereoscopic Endoscope Having Image Transmitting Optical-System and Pupil Dividing Unit that are Axially Movable With Respect to Each Other”, which uses a plural pupil dividing means and one optical channel. U.S. Pat. No. 5,751,341 to Chaleki et al., is directed to a “Stereoscopic Endoscope System”, which is basically a two channel endoscope, with one or two proximal image sensors. A rigid sheath with an angled distal tip could be attached to its edge and be rotated, for full view.
U.S. Pat. No. 5,800,341 to Mckenna et al., is directed to an “Electronically Steerable Endoscope”, which provides different fields of view, without having to move the endoscope, using a plurality of CCD cells and processing means. U.S. Pat. No. 5,825,534 to Strahle, is directed to a “Stereo Endoscope having a Folded Sight Line” including a stereo-endoscope optical channel, having a sight line folded relative to tube axis.
U.S. Pat. No. 5,828,487 to Greening et al., is directed to a “Stereoscopic Viewing System Using a Two Dimensional Lens System” which in general, provides an alternative R-L switching system. This system uses a laterally moving opaque leaf, between the endoscope and the camera, thus using one imaging system. U.S. Pat. No. 5,594,497 to Ahern, describes a distal color CCD, for monocular view in an elongated tube.
The above descriptions provide examples of auto-stereoscopic disclosed techniques, using different switching techniques (Time division multiplexing) and polarization of channels or pupil divisions (spatial multiplexing), all in an elongated shaft. When color image pick up devices are used within these systems, the system suffers from reduced resolution, loss of time related information or a widened cross section.
The issue of color imagery or the issue of a shaft-less endoscope is not embedded into any solution. To offer higher flexibility and to reduce mechanical and optical constraints it is desired to advance the image pick-up device to the frontal part of the endoscope. This allows much higher articulation and lends itself easily to a flexible endoscope. Having a frontal pick up device compromises the resolution of the color device due to size constraints (at this time).
U.S. Pat. No. 5,076,687 to Adelson, is directed to an “Optical Ranging Apparatus” which is, in general a depth measuring device utilizing a lenticular lens and a cluster of pixels.
U.S. Pat. No. 5,760,827 to Faris, is directed to “Pixel Data Processing System and Method for Producing Spectrally-Multiplexed Images of Three-Dimensional Imagery for Use in Stereoscopic Viewing Thereof” and demonstrates the use of multiplexing in color and as such, offers a solution for having a color stereo imagery with one sensor. Nevertheless, such a system requires several sequential passes to be acquired from the object, for creating a stereo color image.
U.S. Pat. No. 5,812,187 to Watanabe, is directed to an Electronic Endoscope Apparatus. This device provides a multi-color image using a monochromatic detector and a mechanical multi-wavelength-illuminating device. The monochromatic detector detects an image, each time the multi-wavelength-illuminating device produces light at a different wavelength.
U.S. Pat. No. 6,306,082 B1 issued to Takahashi, et al., and entitled “Stereoendoscope wherein images having passed through plural incident pupils are transmitted by common relay optical systems”, is directed to an apparatus, namely, an endoscope wherein images, having passed through plural incident pupils, are transmitted by a common relay system, and reconstructed at an observation point to provide a streoscopic image. According to the reference, illuminating light is transmitted by a light guide. Light reflected from the illuminated objects passes through non-superimposed pupils and transmitted to the rear side by a common relay system having a single optical axis. The transmitted images are formed on separate image taking surfaces to allow for a streoscopic image to be formed.
U.S. Pat. No. 5,121,452 issued to Stowe, et al., and entitled “Fiber Optic Power Splitter”, is directed to a method for manufacturing fiber optic power splitters. The fiber optic power splitter is a unitary, single-mode fiber, fused structure which is composed of four, up to seventeen or more fibers, which provide uniform splitting of input optical power among the fibers. The fiber optic power splitter includes a central fiber and identical surrounding fibers, which are sized prior to fusion, such that mutual contact is achieved. In this manner, each of the surrounding fibers touches the central fiber and the neighboring fibers. In this construction, the surrounding fibers are of the same diameter and the central fiber has a different diameter. Optical power input in the central fiber distributes among the surrounding fibers. The optical power output in the central fiber and the surrounding fibers is monitored during the fusion process, and the fusion process is stopped when the desired fraction of the optical power appears in a surrounding fiber.
In Handbook of Optics, Volume 2, McGraw-Hill, Inc., 1995, p. 15-24, Norman Goldberg discusses the concept of stereo cameras. The structure of a stereo camera is based on the parallax difference between the views of the right and the left eyes. The two lenses in the classic stereo camera are spaced about 65 mm apart, in order to form two images of the subject. Another type of stereo camera uses a reflection system of four mirrors or an equivalent prism system, placed in front of the lens of a normal camera, thereby forming two images of the subject (FIG. 15 on p. 15-25 of the Handbook). According to another method, the subject is required to remain stationary while two separate exposures are made and the camera is shifted 65 mm between the two exposures. This method is employed in aerial stereo photography in which two views are made of the ground, the views being made so many seconds apart.
According to another method, the right and left views of the subject are restricted to the respective eye of the viewer, where the right and the left views are polarized at 90 degrees to one another. The viewer wears glasses with polarizing filters oriented such that each eye sees the view intended for it. In a parallax stereogram, the right and left images are sliced into narrow, interlaced right and left strips. The viewer perceives a three-dimensional view of the subject, while viewing the image through a series of vertical lenticular prisms with a matching pitch.
U.S. Pat. No. 5,233,416 issued to Inoue and entitled “Electronic Endoscope System”, is directed to a system which enables the use of an endoscope having either a normal sensitivity or a high sensitivity solid-state image sensor element. The system includes a rotary color wheel, a light source, a condenser lens, the solid-state image sensor element, such as charge coupled device (CCD), an input switch, a first video processor, a second video processor, an output switch, an analog to digital (A/D) converter, a plurality of storage portions, three digital to analog (D/A) converters, an encoder, a first control means, a second control means, a decoder, a master clock and a CCD drive.
The CCD drive is coupled with the CCD, the first control means, and to the master clock. The first control means is coupled with the input switch, the first video processor, the second video processor, the output switch, the A/D converter, the storage portions, the decoder and to the master clock. The CCD is coupled with the decoder and to the input switch. The input switch is coupled with the first video processor and to the second video processor. The output switch is coupled with the first video processor, the second video processor and to the A/D converter. The storage portions are coupled with the A/D converter, to the three D/A converters and to the second control means. The second control means is coupled with the decoder, the master clock, the D/A converters and to the encoder. The three D/A converters are coupled with the encoder.
The condenser lens is located between the light source and the rotary color wheel. The rotary color wheel is located between the condenser lens and a light guide of the endoscope. The rotary color wheel is provided with three filter zones (red, green and blue). The three filter zones are separated by three color-shifting light-blocking zones. Each filter zone is bisected into uniform halves, by an intermediate light-blocking zone.
The input switch switches the system to the first video processor when the normal sensitivity CCD is employed and to the second video processor, when the high sensitivity CCD is employed. The first control means controls the read-out of the signal charges from the CCD and the second control means controls the display of the images. Each of the first control means and the second control means can operate either in a normal sensitivity mode or a high sensitivity mode. The CCD drive produces pulse signals for the CCD, according to the clock signals of the master clock.
The rotary color wheel provides an image to the CCD in red, green and blue, in sequence. When a normal sensitivity CCD is employed, the system switches to the first video processor, and the first control means, the second control means and the CCD drive switch to the normal sensitivity mode. In this mode, the CCD drive enables the read-out of signal charges from the CCD, between every two color-shifting light-blocking zones. The first controller shifts the resulting image to the storage portions, during each color-shifting light-blocking zone. The second controller constructs a color image for each pulse signal, by combining the three images in red, green and blue which are read-out between every two color-shifting light-blocking zones.
When a high sensitivity CCD is employed, the system switches to the second video processor, and the first control means, the second control means and the CCD drive switch to the high sensitivity mode. In this mode, the CCD drive enables the read-out of signal charges from the CCD, between every two color-shifting light-blocking zones, as well as between every two intermediate light-blocking zones. The first controller shifts the resulting image to the storage portions, during each color-shifting light-blocking zone, as well as during each intermediate light-blocking zone. The second controller constructs a color image for each pulse signal, by combining the three images in red, green and blue which are read-out between every two color-shifting light-blocking zones, as well as between every two intermediate light-blocking zones.